Fertilin, originally named PH-30, is a heterodimeric cell surface protein identified on guinea pig, rabbit and human spermatozoa. The alpha subunit has a 22 amino acid hydrophobic peptide that is known to act as a Afusion peptide@ during sperm-egg fusion. The mature fertilin beta subunit has an amino-terminal 90-93 amino acid domain that has sequence homology with a class of known integrin ligands (the snake venom disintegrins), and it is suggested that this domain plays a pivotal role in sperm-egg binding as an integrin-disintegrin interaction. Based on these observations, fertilin and the egg receptor for fertilin could be a potential target for contraception. Some scientists have explored the possibility of using purified fertilin as an antigen for immuno-contraception. Three male guinea pigs received injections of fertilin showing that 100% of the males were infertile. Several control males received injections of adjuvent without protein and none of them were inf erti le. Other studies showed that fertilin beta is expressed only in testis in humans. According to the previous work, we want to design a NH2 terminal 93 amino acid fragment of human fertilin beta (fertilin beta-NTP93) that utilizes the integrin-disintegrin binding domain as an antigen of vaccine and observe the inhibiting ability of sperm-egg binding by anti-human fertilin ?-NTP93 antibody in vitro. FUNDING Mellon Foundation-CONRAD Program (#MFG-97-34) PUBLICATIONS Moreno RD, Ramalho-Santos J, Sutovsky P, Chang E, Schatten G. Molecular membrane marker dynamics during rhesus spermatogenesis Acrosome biogenesis, Golgi apparatus and mitochondrial differentiation. Mol Biol Cell 9:66a, 1998. Ramalho-Santos J, Moreno RD, Sutovsky P, Wessel G, Schatten G. Membrane fusion and fertilization Implications for the presence of SNARE proteins on mammalian spermatozoa. Mol Biol Cell 9:332a, 1998.